Conventionally, there is a widely known semiconductor module produced by encapsulating a plurality of members, such as semiconductor devices, with an encapsulating material such as thermosetting resin. The semiconductor module is used for controlling a motor of a hybrid vehicle, for example.
The semiconductor module needs to be cooled by a predetermined cooler because the semiconductor module heats up in association with switching operation of a semiconductor device (switching element).
JP-A 2001-352023 discloses a semiconductor module includes a pair of metal plates acting as heat spreaders and electrodes, a semiconductor device arranged between the pair of metal plates, and a resin encapsulating the pair of metal plates and the semiconductor device so that the outer surface of each metal plate is exposed.
In the semiconductor module disclosed in JP-A 2001-352023, the semiconductor device is cooled by a cooler (coolant tube) being in contact with the exposed surface of each metal plate through an insulating plate.
In a step for manufacturing the semiconductor module disclosed in JP-A 2001-352023, after encapsulating the pair of metal plates and the semiconductor device with the resin, a part of the resin needs to be removed in order to expose the outer surface of each metal plate.
JP-A 2010-238868 discloses a technique for manufacturing a semiconductor module in which two heat-dissipating surfaces (surfaces to be brought into contact with coolers) are exposed without removing a part of a resin.
The technique disclosed in JP-A 2010-238868 is characterized by providing a movable member which presses one of the heat-dissipating surfaces of a workpiece (a plurality of members such as semiconductor devices) to enter into a cavity where the workpiece is arranged, a first pressure sensor for detecting pressure at which the movable member presses the workpiece, and a second sensor for detecting pressure of the resin in the cavity, and by performing feedback control based on detected values of the sensors so as to keep the pressure at which the movable member presses the workpiece constant.
According to the technique disclosed in JP-A 2010-238868, the workpiece is pressed by the movable member at constant pressure, and thereby a state can be maintained where the plurality of members constituting the workpiece are pressed against each other. Therefore, the semiconductor module can be manufactured without joining the plurality of members constituting the workpiece with joining material such as solder.
Moreover, the workpiece is pressed by the movable member at constant pressure, and thereby the two heat-dissipating surfaces of the workpiece are masked by the movable member and a metal mold even when the cavity is filled with the resin. Therefore, the semiconductor module whose heat-dissipating surfaces are exposed can be manufactured without removing a part of the resin.
However, even if the pressure at which the movable member presses the workpiece is kept constant, the metal mold may open (upper and lower molds move away from each other) due to applying load to the metal mold when the cavity is filled with the resin and the pressure of the cavity is sharply increased. As a result, there is a problem in that the heat-dissipating surfaces are covered with the resin, for example.